Fuse for fire alarms



y 6, 1965 R. J. SMITH 3,192,890

FUSE FOR FIRE ALARMS Filed July so. 1965 a2 /4 /Z 'l) V @1 r 76. 4. 244 000 wi /3 ATTOIQ/VEYS United States Patent 3,192,899 FUSE FOR FIRE ALARMS Randolph J. Smith, Anaheim, Calif., assignor to Interstate Engineering Corporation, Anaheim, Cali, 2 corporation of California Fiied Italy 30, 1963, Ser. No. 293,743 3 Claims. (Ci. 116 -1145) 7 This invention relates to a fuse for fire alarms, and more particularly to the construction and arrangement of the fuse per se, and also'the plate or disc which supports it. It is also particularly adaptable for use in a small self-contained. home fire alarm, but is also capable for use in commercial and industrial establishments.

The fuse unit is adapted for use in connection with an alarm such as the one shown and described in US. Patent No. 2,999,477, issued September 12, 1961, to Verneur Pratt and Edmund C. Pratt, and inasmuch as the alarm per se is shown in said patent, only portions thereof are shown herein for illustrative purposes.

One of the objects of the invention is to provide a fuse unit which will permit the actuation of the alarm when the temperature adjacent the alarm has reached a certain degree of heat, and wherein the fuse unit can be replaced by a householder easily and in the proper manner.

Another object of the invention is to provide means whereby ambient air in the neighborhood of the fuse unit can reach the fuse without obstruction so that the alarm will function in the proper manner.

A further object of the invention is to provide an improved arrangement of a thermally releasable fuse element.

The above and other objects of the invention will more fully appear from the following description in connection with the accompanying drawing:

FIG. 1 is a front elevational view of a fire alarm embodying the invention;

FIG. 2 is an enlarged fragmentary view partially in section, taken on the line 22 of FIG. 1, with the fuse unit shown in full and broken lines to indicate the manner of its mounting on the fuse;

FIG. 3 is .a plan view of the fuse unit in full, and partially in broken lines, to indicate the manner of its mounta;

PEG. 4 is an enlarged fragmentary section taken approximately on the line 44 of FIG. 1.

In the drawing there is shown a fire alarm casing or housing 6, such as the housing shown in the above identified patent. In FIGS. 2 and 4 the housing 6 is shown to have a rear cover plate 8 with a central aperture 19 through which projects a spring-biased control latch'12 in the form of a pin, which when released, will project to 3,192,890 Patented July 6, 1965 ice of FIG. 3, portions of the disc will lie beneath the in Wardly disposed end 16 of said. posts '14 to retain the disc on said posts. This positioning of the-disc on the posts is further insured by insertion of the stationar pin 18 through a circular aperture '28 in the disc 22,-so

that when said disc is in the full line position of FIG. 2, said disc cannot be moved to release the posts 14 from the keyholeapertures 26 while said disc 22 is parallel to the rear closure plate 8 of the housing 6. In order to hold the disc 22 in the full line position of 'FIG. 2, and, prevent its tiling to the broken line position thereof,

a tongue 30 is bent inwardly to contact the rear closure the right, as viewed in FIG. 2, and release the alarm The fuse unit is indicated generally at 20. It includes 7 a disc 22 having a peripheral portion 24 which is flared outwardly relative to the alarm housing 6, as shown in FIGS. 2 and 4. The disc 22 is provided with a pair of L-shaped keyhole apertures 26, the shorter legs of which 7 are of such size and location as to permit passage of the ends '16 of the posts 14, and the longer legs of which are of such width, that when the posts ends 16 are inserted in the shorter legs. of the apertures, and the fuse disc 22 shifted from the broken to the full line position plate of the housing 6 As best shown in FIG. 4, the center of the fuse disc 22 is provided with an aperture in which is a grommet 32. Within the circular aperture, defined by the grommet, is a dished element 34, whose central dished portion lies within the grommet 32, as shown, and whose outer flange 36 lies outwardly of portions of the fuse disc 22. Connection of the dished element 34 with the grommet 32 is provided by means of a solder bond 38. When the fuse unit is mounted on the posts 14 and pin 18, the dished fuse element 34, with its solder bond 38,

bears against the spring-biased alarm latch pin 12, as.

shown in FIGS. 2 and 4. This holds the latch pin in such position that the alarm is not sounding. However, When the ambient temperature in the vicinity of the alarm reaches a certain degree of intensity, the fusible bond 38 will melt and release the dished fuse element 34 from the grommet 32. The pressure of the spring-biased latch pin 12 will eject the dished element 34 from the grommet 32 and away from the fuse disc 22. The springbiased latch being thus released will permit actuation of the alarm, as shown and described in the above identified patent. V

From the foregoing description it will be seen that I have provided a fuse unit for a fire alarm which can be mounted readily upon the alarm, and is so connected with the alarm, that it can be mounted only with the displaceabledished fuse element 34 in such position that it can be pushed from the grommet 32 and ejected away from the fuse disc as desired. If an attempt is made to place the fuse unit on the posts 14 in a reverse position, the keyhole apertures 26 and the circular aperture 28 cannot be properly aligned with their respective posts 14 and pin 18, so that replacement of the fuse is virtually fool-proof.

It will also be seen in'FIGS. 2 and 4' that the flanged peripheral portion 24 of the fuse disc 22 is flared away from the alarm proper, so that the disc 22 does not unnecessarily shield the fusible connection 38 between the grommet 32 and the displaceable fuse element $4.

It is also to be noted that when the displaceable element 34 is inserted'in the grommet 32, it projects only partially through the grommet, so that a drop of solder can'be placed in the grommet, and when heated, will spread to' form the fusible connector 38 in a convenient and effective manner. The fusible connector 38 can be made of different suitable alloys so that fuse units can be produced to set off the alarm at different desired temperatures.

While I have described the fuse unit in connection with i the self-contained alarm of the above patent, it should be understood that it could of'course be used in connection with other types of fire alarm devices and systems. It should also be understood that various changes can be made in the form, details, arrangement and proportions of the various parts, without departing from the spirit of the invention.

I claim: V r I r '1 In a fire alarm, a housing, a spring-biased control latch extending outwardly from the housing and movable outwardly relative thereto, a pair of spaced fuse elements supporting posts carried by and extending outwardly from said housing adjacent said control latch and having enlargements on their outer ends; a fuse element having a thermally releasable portion engageable with said control latch to hold it against the bias of its spring, said fuse element having spaced keyhole apertures to accommodate said supporting posts, each aperture having a portion larger than the enlargement on its respective post, and a portion smaller than the enlargement to permit locking of the fuse element on the posts under the pressure of said spring-biased control latch.

2. The structure in claim 1, and said housing having a pin extending therefrom, said fuse element having another aperture therein to receive said pin, said pin and said another aperture comprising indexing means for proper association of said keyhole apertures with said fuse element supporting posts.

3. The structure in claim 1, and said fuse element having a bendable member extending therefrom inwardly to and engaging said housing, and said keyhole apertures being located on a line crossing a line between said another aperture and said bendable member to prevent accidental dislodgement of said fuse element.

References Cited by the Examiner UNITED STATES PATENTS 2,411,629 11/46 Lane 85l 2,999,477 9/61 Pratt et al 116-106 3,079,886 3/63 Green 116-112 LOUIS I. CAPOZI, Primary Examiner. 

1. IN A FIRE ALARM, A HOUSING, A SPRING-BIASED CONTROL LATCH EXTENDING OUTWARDLY FROM THE HOUSING AND MOVABLE OUTWARDLY RELATIVE THERETO, A PAIR OF SPACED FUSE ELEMENTS SUPPORTING POSTS CARRIED BY AND EXTENDING OUTWARDLY FROM SAID HOUSING ADJACENT SAID CONTROL LATCH AND HAVING ENLARGEMENTS ON THEIR OUTER ENDS, A FUSE ELEMENT HAVING A THERMALLY RELEASABLE PORTION ENGAGEABLE WITH SAID CONTROL LATCH TO HOLD IT AGAINST THE BIAS OF ITS SPRING, SAID FUSE ELEMENT HAVING SPACED KEYHOLE APERTURE TO ACCOMMODATE SAID SUPPORTING POSTS, EACH APERTURE HAVING A PORTION LARGE THAN THE ENLARGEMENT ON ITS RESPECTIVE POST, AND A PORTION SMALLER THAN THE ENLARGEMENT TO PERMIT LOCKING OF THE FUSE ELEMENT ON THE POSTS UNDER THE PRESSURE OF SAID SPING-BIASED CONTROL LATCH. 